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Wiley InterScience | ||||||||||||||||||||||||||||||
  Conservation BiologyVolume 20 Issue 5, Pages 1499 - 1506 Published Online: 30 Jun 2006 ©2010, Society for Conservation Biology Published on behalf of the Society for Conservation Biology
Abstract | References | Full Text: HTML, PDF (Size: 247K) | Related Articles | Citation Tracking  Using Scalar Models for Precautionary Assessments of Threatened Species Copyright 2006 Society for Conservation Biology KEYWORDS age structure • count-based PVA • extinction risk • matrix models • population viability analysis • threatened species KEYWORDS análisis de viabilidad poblacional • análisis de viabilidad poblacional basada en conteos • especies amenazadas • estructura de edades • modelos matriciales • riesgo de extinción ABSTRACTAbstract: Scalar population models, commonly referred to as count-based models, are based on time-series data of population sizes and may be useful for screening-level ecological risk assessments when data for more complex models are not available. Appropriate use of such models for management purposes, however, requires understanding inherent biases that may exist in these models. Through a series of simulations, which compared predictions of risk of decline of scalar and matrix-based models, we examined whether discrepancies may arise from different dynamics displayed due to age structure and generation time. We also examined scalar and matrix-based population models of 18 real populations for potential patterns of bias in population viability estimates. In the simulation study, precautionary bias (i.e., overestimating risks of decline) of scalar models increased as a function of generation time. Models of real populations showed poor fit between scalar and matrix-based models, with scalar models predicting significantly higher risks of decline on average. The strength of this bias was not correlated with generation time, suggesting that additional sources of bias may be masking this relationship. Scalar models can be useful for screening-level assessments, which should in general be precautionary, but the potential shortfalls of these models should be considered before using them as a basis for management decisions. ABSTRACTResumen: Los modelos poblacionales escalares, comúnmente conocidos como modelos basados en conteos, se basan en datos de series de tiempo de tamaños poblacionales y pueden ser útiles para evaluaciones de riesgo a nivel de diagnóstico cuando no hay disponibilidad de datos para modelos más complejos. Sin embargo, el uso apropiado de tales modelos con fines de gestión requiere entender los sesgos inherentes que pueden existir en estos modelos. A través de una serie de simulaciones, que comparaban predicciones del riesgo de extinción en modelos escalares y matriciales, examinamos si las discrepancias se pueden originar de las diferentes dinámicas mostradas debido a la estructura de edades y el tiempo generacional. También examinamos modelos escalares y matriciales de 18 poblaciones reales para determinar patrones potenciales de sesgos en las estimaciones de viabilidad poblacional. En el estudio simulado, el sesgo preventivo (i.e., sobreestimación de los riesgos de declinación) de los modelos preventivos incrementó en función del tiempo generacional. El ajuste entre los modelos escalares y matriciales de las poblaciones reales fue pobre, los modelos escalares predijeron significativamente mayor riesgo de extinción en promedio. La robustez de este sesgo no se correlacionó con el tiempo generacional, lo que sugiere que esta relación puede estar enmascarada por fuentes adicionales de sesgo. Los modelos escalares pueden ser útiles para evaluaciones a nivel diagnóstico, que en general deberían ser preventivas, pero las deficiencias potenciales de estos modelos deberían ser consideradas antes de utilizarlos como base para decisiones de manejo. Paper submitted August 11, 2005; revised manuscript accepted December 28, 2005. | 
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Free Article from Conservation Biology |  |
The article One Hundred Questions of Importance to the Conservation of Global Biological Diversity is now available FREE online. | |
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Conservation Letters |
Conservation Letters is a new, online-only scientific journal publishing empirical and theoretical research with significant implications for the conservation of biological diversity. |
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Conservation |
Conservation is a sophisticated, readable, and utterly practical magazine for people who are serious about conservation. |
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 | New Perspectives on Psychology and Human–Animal Interactions |
This issue of Journal of Social Issues focuses on human attitudes toward the use of other species, the effects of relationships with companion animals on human health and well-being, and the ethical and policy implications of our interactions with other species. | |
